This invention relates to improvements in a cooling device for cooling an electric device through the utilization of a so-called vapor cooling system.
Cooling systems utilizing the phase change exhibited by condensible coolants such as FREON (trade mark) boilable and condensible adjacent to room temperature and under suitable pressures are enabled to handle heat having an extremely high thermal flux on the thermally conducting surface having a very small area with a low temperature differential. Thus such cooling systems make it possible to provide cooling devices having an excellent cooling characteristic and which are small-sized as compared with cooling systems employing coolants such as air or oils effecting no phase change. In the past, open coolant systems employing, for example, water were used to cool electric devices such as vacuum tubes, but the cooling of electric devices utilizing the phase change of condensible coolant and more particularly the boiling phenomenon thereof has been rapidly embodied in closed system cooling devices employing electrically insulating, condensible coolants such as FREON (trade mark) which have been put to practical use for electric devices having a really high capability.
Conventional vapor cooling devices have comprised a plurality of alternate heat generation elements such as semiconductor elements in compressive contact relationship with heat dissipation plates and immersed into an amount of a liquid coolant such as above described charged in a vapor cooling container. The container has been connected to fluid communication relationship with a condenser disposed thereabove through a connection tube. Heat generated by the semiconductor elements boils the liquid coolant into its vapor phase. The vaporized coolant is moved upwardly through the connection tube to enter the condenser where it is condensed into the liquid phase. Then the liquid coolant drops upon the liquid coolant within the container. Such vapor cooling devices have excellent cooling characteristics but have been disadvantageous in that upon replacing any one of the semiconductor elements, the heat dissipation blocks or their accessories by a new one, the cooling container is necessarily broken open to gain access thereto because the container, the condenser and the connection tube forms a closed coolant loop.
In order to eliminate this disadvantage, it has been already proposed to carry a semiconductor device between a pair of vapor cooling containers such as above described to maintain them in compressive contact relationship. Each of the vapor cooling containers has communicated with one condenser through an individual connection tube as above described. This measure has been disadvantageous in that with the semiconductor device having a high capability, sufficient cooling is not accomplished. This is because the condensed coolant returned to each of the vapor cooling containers is generally a very small amount so that the liquid coolant as passed through the connection tube can be carried up by the large amount of vapor coolant from the vapor cooling container ascending along the same tube. Thus the container is emptied of the liquid coolant whereupon the normal cooling operation is suspended. As a result, the liquid coolant thrown up drops into the container to again boil resulting in an intermittent cooling operation and therefore in insufficient cooling of the semiconductor device. This disadvantage can be eliminated by increasing the cross sectional area of the connection tubes, but this measure is attended by various limitations.
Accordingly it is an object of the present invention to provide a new and improved vapor cooling device for an electric device including a cooling system which is stable in operation wherein the disadvantages of the prior art as above described are eliminated by a simple construction.